Sensors are needed for a variety of applications. For example, pump applications, such as sump, dewatering, sewage, utility, effluent and grinder pumps, can use sensors to determine when the pump should be turned on and/or turned off. Conventional sump pumps generally include a pump having a mechanical switch connected to a float mechanism for controlling a liquid level in a reservoir. The float mechanism is disposed within the reservoir and adapted to travel on the surface of the liquid as the liquid rises and falls. Typical float mechanisms are mechanically connected to the switch and according to the position of the float relative to the pump, the switch controls power to the pump.
In one configuration, the mechanical connection between the switch and the float includes a flexible tether. As the float travels up or down on the surface of the liquid in the reservoir, the orientation of the flexible tether relative to the switch changes. Another typical form of a float mechanism includes one or more rods or interconnected linkages. Similar to the tether, the rods or linkages are configured to allow the float to travel freely with the rising or falling of the surface of the liquid in the reservoir. In either of these configurations, once the float reaches a predetermined upper limit, the tether, rod, or linkage transfers a mechanical force to flip the switch, thereby completing the circuit and activating the pump. Conversely, when the liquid level and the float reach a predetermined lower limit, the tether, rod, or linkage transfers a mechanical force to the switch in an opposite direction, thereby interrupting the circuit and deactivating the pump.
A shortcoming of the above-described sump pump float switch mechanisms is that they are inclined to experience mechanical failure. Sometimes mechanical failure occurs due to a deterioration of the mechanical connection between the float and the switch. Other times, the mechanical failure may occur due to objects in the reservoir that restrict or hinder the proper operation of the float mechanism.
A further known sump pump switching mechanism includes a resistance switching mechanism. Resistance switching mechanisms include a pair of electrodes exposed in the liquid in the reservoir. As the level of the liquid in the reservoir changes relative to the electrodes, the electrical resistance between the two electrodes changes. Based on the change in resistance between the two electrodes, a controller activates or deactivates the pump. A shortcoming of resistance type switch mechanisms is that the electrodes are exposed to the liquid and tend to be vulnerable to corrosion. Once corroded, the electrodes fail to generate accurate resistances that the controller expects and the controller fails to operate properly.
A still further known sump pump switching mechanism includes a capacitance switching mechanism. Capacitance switching mechanisms generally include a controller, an upper capacitor having two electrodes, and a lower capacitor having two electrodes. The upper and lower capacitors operate substantially independent of each other. When the level of the liquid reaches the upper capacitor, the controller detects a capacitance across both capacitors and activates the pump. The controller continues to activate the pump as the level of the liquid in the reservoir drops. Once the level of the liquid drops below the lower capacitor, the controller detects no capacitance across the lower capacitor and deactivates the pump. One shortcoming of such capacitance-based switching mechanisms is the reliance on multiple capacitors. Failure of one of the upper and lower capacitors may detrimentally affect the proper operation of the entire sump pump.
In other known sump pump applications, magnetic switching mechanisms, such as Hall Effect sensors or switches, are used to detect water levels and operate a pump. For example, in some applications, a float is used to raise a magnet to an upper magnetic sensor at which point the pump is turned on. When the water level drops the float descends down to a lower magnetic sensor at which point the pump is turned off. A shortcoming of such magnetic sensors is that they again require moving parts and are inclined to experience mechanical failure, such as that discussed above with respect to tethers.
Accordingly, it has been determined that a need exists for an improved sensor and method and apparatus for controlling a pump using same which overcome the aforementioned limitations and which further provide capabilities, features and functions, not available in current sensors and pumps.